1. Field of the Invention
The present invention relates to an inspection data analyzing apparatus for use during each semiconductor processing step, i.e., during in-line inspection of a semiconductor.
2. Description of the Background Art
During conventional in-line inspection of a semiconductor, an inspection apparatus detects positional coordinate data (i.e., XY-coordinate data) of a defect within a semiconductor wafer, and based on the detected defect data, the inspection apparatus or an inspection data analyzing apparatus displays the position of each detected defect as a dot on a display apparatus which is included in the inspection apparatus or the inspection data analyzing apparatus. FIG. 24 shows an example of a map display on such a display apparatus. As shown in FIG. 24, a conventional inspection data analyzing apparatus displays dots DT at positions where defects are detected, so as to inform a user of information expressing a distribution of the detected defects.
In addition, from the positional data regarding the detected defects which are supplied by the inspection apparatus, the conventional inspection data analyzing apparatus calculates data which express the number of detected defects for each inspection step, which is obtained by classifying the detected defect data by inspection step numbers upon detection of a first defect. The conventional inspection data analyzing apparatus then processes the resulting data into a histogram and outputs the histogram to the display apparatus. In other words, the inspection apparatus inspects the same wafer repeatedly every time manufacturing of a semiconductor proceeds to the next step while XY-coordinate data on each detected defect are verified within an optional tolerance range and inspection data for the respective steps are overlapped, thereby creating the data which express the number of detected defects for the respective steps which are classified by the numbers assigned to the respective steps which are precedent to the current step. FIG. 25 shows an example of a displayed histogram regarding the number of detected defects for the respective steps obtained in this manner.
In FIG. 25, the figures in the histogram regarding the number of detected defects for the respective steps denote the number which is assigned to each manufacturing step or each inspection step. For instance, n12 defects are among defects which are created at the manufacturing step 1 are still detected during the inspection step 2 even after the manufacturing step 2 is completed. During the inspection step 3, n13 defects are among the defects which are created at the manufacturing step 1 and n23 defects are among defects which are created at the manufacturing step 2 are still detected even at the end of the manufacturing step 3.
Thus, the histogram in FIG. 25 shows a user at which step a detected defect appeared for the first time.
However, a user finds the following problems with the conventional inspection data analyzing apparatus.
First, since a map displaying the detected defects allows a user to read only the detected positions of the detected defects, the user cannot sufficiently read the situation in which the defects were created only from the information available from the map. Thus, when the user needs to determine which defect is to be studied to investigate a dust source or to solve a process-related problem, the map as it is conventionally displayed cannot sufficiently supply information needed for such judgement and is virtually almost useless.
Second, users in general cannot accurately read the total number of defects which exist in the wafer as a whole from the histogram as it is conventionally displayed. That is, since manufacturing steps such as a film formation step and an etching step are repeatedly executed during semiconductor processes, the accuracy of detecting defects varies among inspection steps. Due to this, even when defects are detected at one inspection step, after the next manufacturing step, the detected defects may not be detected at the next inspection step. Although this causes no problem if the detected defects completely disappear during the next manufacturing step, in reality, it is likely that the detected defects become invisible through the next manufacturing step such as a film formation step and reappear after a further manufacturing step. Therefore, the largest problem resides at the manufacturing step where such defects which reappear later are initially created. For semiconductor processes, it is important to find such a manufacturing step.
Meanwhile, an experienced user is well aware of such nature as above of defects. To an experienced user, the information obtainable from the conventional histogram in FIG. 25 may be sufficient. However, to ordinary users, it is extremely difficult or impossible to read information related to defects which disappear once and appear again later from the histogram in FIG. 25. When using the conventional inspection data analyzing apparatus, ordinary users are very likely to misjudge that an excellent quality wafer is manufactured with only a few defects created during the respective steps.
These problems can be attributed to a fact that conventional inspection apparatuses and conventional inspection data analyzing apparatuses are developed mainly from a manufacturer's point of view and that those apparatuses do not meet the demands from ordinary users.